When cave vines generate too close to the ground the block below them gets replaced with stone

When cave vines generate too close to the ground the block below them gets replaced with stone/granite etc. while it should be clay or moss, this is likely unintended behaviour.

How to reproduce:
Create a large biome's world with seed: -240861352427657586
/execute in minecraft:overworld run tp @s 767.80 16.50 854.78 -487.20 47.25
/execute in minecraft:overworld run tp @s 724.50 25.00 772.50 -350.70 24.90
Might take a few attempts due to 219200

Note: To create a large biome world you need to create it in 1.17 first then upgrade it in 21w39a